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SubjectDifferences between FreeBSD and Linux system call mechanism
in freebsd-current Terry Lambert wrote:

> Linux uses a call-gate based kernel entry, which is TSS based, and
> therefore takes more CPU cycles on a contect switch than strictly
> required. The FreeBSD mechanism for kernel entry (and subsequet
> context switch) is threfore more efficient than that used by Linux.

I'm starting to wonder. Terry normally knows what he is talking about,
but this posting seems to contain various mistakes:

1) Linux system calls are done using software interrupt 0x80 on ia32.
Does this qualify as a "call-gate based kernel entry"?
2) I don't see the connection between kernel entry and TSS based task
switch. Mingo already has patches that replace the current TSS method
with software based context switchs.
3) I'm not sure about Terrys definition of "efficient", but if he means
required CPU cycles I thought that there were not that many left in
Linux that FreeBSD could be better. Has anybody hard numbers for both
kernels?

--
Regards
Joerg
GMD-IPSI, Dolivostr. 15, Zimmer 120, D-64293 Darmstadt
+49-6151-869-786 (Phone), -818 (FAX)

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